From: Chris Redpath <[email protected]> When lower capacity CPUs are load balancing and considering to pull something from a higher capacity group, we should not pull tasks from a cpu with only one task running as this is guaranteed to impede progress for that task. If there is more than one task running, load balance in the higher capacity group would have already made any possible moves to resolve imbalance and we should make better use of system compute capacity by moving a task if we still have more than one running.
cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Chris Redpath <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index aac7b9155bc4..5d612d3906d5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8796,6 +8796,17 @@ static struct rq *find_busiest_queue(struct lb_env *env, capacity = capacity_of(i); + /* + * For ASYM_CPUCAPACITY domains, don't pick a cpu that could + * eventually lead to active_balancing high->low capacity. + * Higher per-cpu capacity is considered better than balancing + * average load. + */ + if (env->sd->flags & SD_ASYM_CPUCAPACITY && + capacity_of(env->dst_cpu) < capacity && + rq->nr_running == 1) + continue; + wl = weighted_cpuload(rq); /* -- 2.7.4
